Soil Organic Matter, CEC, and Moisture Sensing with a Portable NIR Spectrophotometer

Abstract

Soil reflectance data were collected with a portable near infrared (NIR) spectrophotometer and were correlated with soil organic matter content in laboratory and field tests. Laboratory calibrations yielded an r2 of 0.89 and a standard error of prediction of 0.40% organic matter with 30 representative Illinois soils at 1.5 MPa and 0.033 MPa moisture tension levels. Limited in-furrow field operation produced much higher errors, due to the movement of soil past the sensor during data acquisition. Estimation of cation exchange capacity (CEC) and soil moisture content was also accomplished in the laboratory.